Power regulators such as switch-mode voltage regulators are widely used in various electronic devices. In the presently existing switch-mode voltage regulators, a high voltage signal used to drive a high side switch may be needed. Thus, a bootstrap circuit will be applied to provide the high voltage signal, wherein the bootstrap circuit may comprise a bootstrap capacitor having a large capacitance. Generally, in order to save size and improve efficiency of the switch-mode voltage regulators, most of the components of the switch-mode voltage regulators are integrated on a monolithic die. However, the bootstrap capacitor is too large to integrate. For example, FIG. 1 illustrates a switch-mode voltage regulator 50 having a voltage converter IC 60 and an external bootstrap capacitor CBO. As shown in FIG. 1, the voltage converter IC 60 has an input pin IN, a ground pin GND, a bootstrap pin BST, a switching pin SW and a feedback pin FB. The bootstrap capacitor CBO may be coupled externally between the switching pin SW and the bootstrap pin BST, which can result in large package size and lower efficiency.